1. Field of the Invention
The present invention relates to a laser condensing optical system and a laser processing device which condense a laser beam at different positions in a medium.
The present invention also relates to a laser processing device which can change the position of a beam source while maintaining constant intensity and intensity distribution of light which is incident on a pupil face of an optical system. The present invention particularly relates to an ideal laser processing device which can condense a laser beam at positions of different depths in a medium, or a laser processing device which is suitable for changing a condensing position.
2. Description of the Related Art
Currently, laser beams are used in various fields, and various types of devices using laser beams are being developed. One example is a processing device which uses a laser beam to cut a target for processing, such as a semiconductor wafer or glass. This processing device includes a condensing optical system which, by condensing a laser beam emitted from a laser beam source, generates a modifying layer or the like in a medium and thereby cuts it. When cutting, since targets for processing have various thicknesses, the laser beam is not always condensed at the same depth, and must be condensed at different thicknesses in accordance with the thickness of the target for processing. That is, there is a demand to condense at sections of different depths in a medium.
Various conventional techniques are used to condense light in sections of different thicknesses such as those mentioned above while correcting spherical aberration and suppressing change in the condensing performance.
For example, in one such technique, parallel plate glasses of different thicknesses are removably attached at the tip of a condensing optical system such as an objective lens.
There is also a conventional objective lens with a correction ring for microscope which successfully corrects aberration over an ultra-wide field, having a magnification of approximately 40-power and an NA (numerical aperture) of 0.93 (e.g. see Japanese Unexamined Patent Application, First Publication No. H05-119263 (FIG. 1 etc.)).
There is also an optical system which corrects spherical aberration by moving a spherical aberration correcting optical system of a no power lens in the optical axis direction (e.g. see Japanese Unexamined Patent Application, First Publication No. 2003-175497 (FIG. 1 etc.)).
Furthermore, FIG. 20 shows a microscope device in which spherical aberration is corrected by arranging a spherical aberration correcting lens 232 between an objective lens 230 and a light source 231, and moving the spherical aberration correcting lens 232 along the optical axis (e.g. see Japanese Unexamined Patent Application, First Publication No. 2001-83428 (FIG. 1 etc.)).